Multi-thread chain stitch sewing machine with seam ravel preventing apparatus

ABSTRACT

A needle plate base in a multi-thread chain stitch sewing machine with a seam ravel preventing apparatus is divided into a left needle plate base for attaching a needle plate thereto and supporting a swinging support shaft of a thread hanging hook; and a right needle plate base for fixedly supporting a stopper member and a thread handling air cylinder and a stopper air cylinder. The right needle plate base is fastened to a sewing machine bed. The left needle plate base is fastenably and unfastenably fastened to an upper surface of the bed via screw members. Adjustment of stitch performation, and maintenance, e.g., replacement of various kinds of components stored inside the bed, can extremely easily and simply be carried out without having much trouble and requiring labor and time, and therefore, the stitch performation and predetermined ravel preventing function can be constantly surely reproduced.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Stage application of International Application No. PCT/JP2012/070714, filed on Aug. 7, 2012 and claims priority of Japanese application serial number 2011-183121 filed on Aug. 8, 2011, all of which are incorporated herein by reference in their entireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a multi-thread chain stitch sewing machine typically represented by a horizontal tube type multi-thread chain stitch sewing machine, which forms multi-thread chain stitch seams with a needle thread and a looper thread, and is provided with a seam ravel preventing apparatus for preventing a ravel from occurring in a certain portion at the end of sewing of multi-thread chain stitch seams.

2. Background Art

The horizontal tube type multi-thread chain stitch sewing machine includes one or more needles moving up and down while holding a needle thread, and a looper which moves forward and backward while holding a looper thread in a direction substantially orthogonal to a vertical movement path of the needle. In this sewing machine, a needle thread loop formed below a needle plate by the needle is caught by the forward movement of the looper, and the needle thread is interloped by the looper thread held by the looper, thereby forming the multi-thread chain stitch seams.

General multi-thread chain stitch seams formed by the multi-thread chain stitch sewing machine have suffered from the following problem. That is, as shown in FIG. 20, when an end portion of a looper thread 10 cut at the end of sewing is pulled in a direction indicated by the arrow in FIG. 20, the looper thread 10 slips out of the last needle thread loops 20 a and 20 b respectively formed by needle threads 20 and 20. The slipping-out is likely to propagate toward a sewing start point, thus causing ravel throughout the entirety of the seams.

This ravel occurs similarly in multi-thread chain stitch seams formed with a needle thread or two or more needle threads and a looper thread.

For the purpose of preventing the ravel peculiar to the seams formed by the multi-thread chain stitch sewing machine, the present applicant has already developed and filed the patent application related to the following multi-thread chain stich sewing machine with a ravel preventing apparatus (hereinafter referred to as the technique described in an already-filed patent application of the present applicant).

The ravel preventing apparatus for the multi-thread chain stitch sewing machine of the technique described in the already-filed patent application (A two-needle sewing machine is described here.) is configured by including (i) needles 2 and 2 (refer to FIGS. 11 to 17) moving up and down while holding the needle threads 20 and 20, with respect to needle drop positions A and A set with a distance laterally interposed therebetween at a substantially middle portion of a needle plate P as shown in FIGS. 21 to 23; (ii) a looper 1 (refer to FIGS. 11 to 17) which can perform forward and backward movements while holding a looper thread 10 in an arrangement direction of the needle drop positions A and A, and catches needle thread loops 20 a and 20 b formed below the needle plate P during the forward movement; (iii) a thread hanging hook 3 which can perform approach and departure movement with respect to the looper 1, and swings around a vertically extending support shaft 30 between a standby position away from the looper 1 as shown in FIG. 21, and a thread hooking position adjacent to the looper 1 as shown in FIG. 23, in a plane substantially parallel to the needle plate P, and a thread handling air cylinder (hereinafter including one called thread handling cylinder) 32 as a hook actuator for drivingly swinging the thread hanging hook 3 to the standby position and the thread hooking position; (iv) a swing lever 9 which is disposed at a position farther away from the needle plate P than the thread hanging hook 3, and swings around a vertically extending support shaft 90 in the plane substantially parallel to the needle plate P so that the needle thread loops 20 a and 20 b caught at the thread hooking position by the thread hanging hook 3 are held at a hold position between the thread hooking position and the standby position, and a stopper lever 4; (v) a stopper air cylinder (hereinafter including one referred to as a stopper cylinder) 42 as a stopper actuator for drivingly swinging the stopper lever 4 from an engaging position at which the stopper lever 4 engages with a part of the swing lever 9, to a retracted position away from the engaging position; (vi) a connecting rod 35 for interlockingly connecting the thread hanging hook 3 and the swing lever 9; and (vii) a control section 8 (refer to FIG. 8) which performs selective action control of the thread handling cylinder 32 and the stopper cylinder 42 after terminating the normal sewing, and allows the needle thread loop 20 b, one of those caught at the thread hooking position by the thread hanging hook 3, to be held at the hold position so that a sewing action for at least one stich is performed while maintaining the hold state.

Structural members and structural portions in the ravel preventing apparatus of the multi-thread chain stitch sewing machine of the technique described in the already-filed patent application by the present applicant, which are identical to or corresponding to a ravel preventing apparatus as an embodiment of the present invention described later, are identified by the same reference numerals as in the embodiment of the present invention, and their respective detailed descriptions are omitted here.

In the already-filed patent application by the present applicant, after terminating the normal sewing, the foregoing sewing action for a stitch is performed by controlling the actions of the thread hanging hook 3, the stopper lever 4, and the swing lever 9 via the control section. Thereby, as shown in FIG. 18, the looper thread 10 passes through the final needle thread loop 20 a on the right side (the left side in FIG. 18) that is formed finally in the multi-thread chain stitch seams M on a rear surface of a fabric, and is turned back in front of the needle thread 20, which slips out toward the rear surface of the fabric when sewing one stitch for preventing ravel, and is then cut at a certain position after passing through the right final needle thread loop 20 a. On the other hand, the needle thread 20 on the left side (the right side in FIG. 18), which slips out toward the rear surface of a fabric when sewing the one stitch, passes through a final needle thread loop 20 b finally formed at the end of the normal sewing on the rear surface of the fabric, and allows the final needle thread loop 20 b to be selflooped, thereby forming chain stitch seams. Consequently, the looper thread 10 enters into a state of being pressed between the left needle thread 20 and the left final needle thread loop 20 b, as shown in FIG. 18.

Although FIG. 18 shows a state in which the left final needle thread loop 20 b and the needle thread 20 are loose in order to clarify entanglement between the two, the actual left final needle thread loop 20 b is strongly tightened after the needle thread 20 passes therethrough, thereby entering into a state similar to that of the right final needle thread loop 20 a, as shown in FIG. 19. The looper thread 10 is strongly pressed between the needle thread 20 and the left final needle thread loop 20 b, and is restricted in a state of being hung over the left final needle thread loop 20 and the left needle thread loop 20 c formed immediately before. This restriction is maintained even when the looper thread 10 is subject to a force exerted from any direction, as shown in FIG. 19, thereby surely preventing occurrence of ravel peculiar to the multi-thread chain stitch seams M.

Thus, the multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to the technique described in the already-filed patent application by the present applicant is capable of effectively preventing the occurrence of ravel peculiar to the multi-thread chain stitch seams. However, the following problem that needs improvement remains unsolved in the multi-thread chain stitch sewing machine with the seam ravel preventing apparatus.

That is, in the technique described in the already-filed patent application by the present applicant, as shown in FIGS. 21 to 23, the thread hanging hook 3, the stopper lever 4, the swing lever 9, the thread handling cylinder 32, the stopper cylinder 42, which are the structural elements of the seam ravel preventing apparatus, are supported to a laterally long and large needle plate base 11 which has the needle plate P attached thereto, and is fastened to an upper surface of a sewing machine bed. Specifically, the support shaft 30 for the swing of the thread hanging hook 3 is supported at a position in the vicinity of the rear side of the needle plate P on the left side of the needle plate base 11. On the other hand, the stopper lever 4, the swing lever 9, the thread handling cylinder 32, and the stopper cylinder 42 are respectively supported at positions away from the needle plate P on the right side of the needle plate base 11. Also, the connecting rod 35 is connected between a front end portion of the swing lever 9 and a front end portion of an extended part 3 c extended so as to be folded forward from the support shaft 30 for swinging the thread hanging hook 3. Reference numeral 6 in FIGS. 21 to 23 denotes a looper thread holder fastened together with the thread hanging hook 3 via fixing screws 60 and 60.

Thus, in the multi-thread chain stitch sewing machine of the technique described in the already-filed patent application by the present applicant, all the structural elements of the seam ravel preventing apparatus are supported by the laterally long and large needle plate base 11. Therefore, if after the needle plate base 11 with the components of the ravel preventing apparatus installed and supported thereon is attached to the upper surface of the sewing machine bed, it becomes necessary to adjust, for example, stitch performation by correcting the positions and the loci of actions of members performing sewing action which are stored below the needle plate base 11 and inside the sewing machine bed, such as the looper and the members for actuating the looper, or it becomes necessary to perform maintenance, such as replacement of various kinds of components incorporated into the sewing machine bed, an operating space that is wide enough to perform the adjustment and the maintenance cannot be ensured only by removing the needle plate P. Hence, to ensure the wide operating space, it becomes necessary to perform an operation requiring labor in which predetermined adjustment and maintenance are carried out after the entirety of the long large needle plate base 11 is temporarily removed from the sewing machine bed, and thereafter the entirety of the long and large needle plate base 11 is reattached to the sewing machine bed.

Particularly, air tubes 33 and 43 for supplying operating air to the thread handling cylinder 32 and the stopper cylinder 42 are respectively connected to these two cylinders. Therefore, it becomes necessary to perform extremely bothersome and time-consuming operation in which when removing and attaching the needle plate base 11, these two air tubes 33 and 43 are pulled out from inside the sewing machine bed so that both do not obstruct the removal and attachment operations, and after these operations, both air tubes are pushingly returned to the inside of the sewing machine bed. However, unless the bothersome and time-consuming adjustment and maintenance operations are carried out, there is a probability that the stitch performation is deteriorated, and a predetermined ravel preventing function cannot be reproduced. This necessitates the extremely bothersome and time and labor consuming operations. This problem also still remains unsolved.

CITED REFERENCES

Japanese Patent Application No. 2011-016821

Japanese Patent Application No. 2011-115174

SUMMARY OF THE INVENTION Technical Problem

The present invention has been made in view of the foregoing circumstances, and an object thereof is to provide a multi-thread chain stitch sewing machine with a seam ravel preventing apparatus, with which the occurrence of ravel peculiar to the multi-thread chain stich seams can effectively be prevented, and the maintenance, such as the adjustment of stitch performation by the position correction of the members for performing sewing action, and the replacement of various kinds of components stored inside the sewing machine bed can extremely easily and simply be carried out without having much trouble and requiring labor and time, thereby allowing the stitch performation and predetermined ravel preventing function to be constantly surely reproduced.

Solution to Problem

In order to achieve the above object, the multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to the present invention includes a needle moving up and down while holding a needle thread; a looper which is movable forward and backward while holding a looper thread in a direction substantially orthogonal to a vertical movement path of the needle, and catches a needle thread loop formed below a needle plate by the needle during a forward movement; and a needle plate base having the needle plate attached thereto and being attached to an upper surface of a sewing machine bed. The multi-thread chain stitch sewing machine forms multi-thread chain stitch seams on a fabric by allowing the looper to catch the needle thread loop formed below the needle plate by the needle, and then by interlooping the needle thread with the looper thread held by the looper. The multi-thread chain stitch sewing machine with the seam ravel preventing apparatus includes (A) a needle thread holding mechanism having (i) a thread hanging hook which is approachable and departable with respect to the looper, and swings around a vertically extending support shaft in a plane substantially parallel to the needle plate between a standby position away from the looper and a thread hooking position close to the looper, and (ii) a hook actuator for drivingly swinging the thread hanging hook to the standby position and the thread hooking position; (B) a stopper mechanism having (iii) a stopper member which is disposed at a position farther away from the needle plate than the thread hanging hook of the needle thread holding mechanism, and permits temporary suspension and unsuspension of a swing of the thread hanging hook from the hooking position to the standby position so that the needle thread loop caught by the thread hanging hook at the thread hooking position is held at a hold position between the thread hooking position and the standby position, and (iv) a stopper actuator for performing the suspension and the unsuspension of the stopper member; (C) a connecting member for interlockingly connecting the thread hanging hook of the needle thread holding mechanism and the stopper member of the stopper mechanism; and (D) a control section which controls the needle thread holding mechanism and the stopper mechanism in association with a vertical movement of the needle, forward and backward movements of the looper, and feed of the fabric, so that the looper is moved forward after a normal sewing is terminated, the thread hanging hook of the needle thread holding mechanism is brought near the looper, the needle thread loop caught at the thread hooking position is moved to the hold position, a resulting state is maintained until the needle descends through the needle thread loop caught by the looper, and thereafter, a sewing action for at least one stitch is performed.

The needle plate base is divided into two sections: a left needle plate base for attaching a needle plate thereto and supporting a swinging support shaft of a thread hanging hook; and a right needle plate base for fixedly supporting the stopper member and the hook actuator and the stopper actuator. The right needle plate base is fastened to the sewing machine bed. The left needle plate base is fastenably and unfastenably fastened to an upper surface of the sewing machine bed via screw members.

Advantageous Effects of Invention

In the multi-thread chain stitch sewing machine with the seam ravel preventing apparatus having the foregoing characteristic features, after normal sewing is terminated, the looper is moved forward, and the thread hanging hook of the needle thread holding mechanism is brought near the looper, and the needle thread loop caught by the looper is moved to the hold position and, in this state, the sewing action for at least one stitch is performed. Accordingly, the preceding needle thread loop is self-looped with the needle thread held by the descending needle, and the looper thread is held down by the self-looped portion, thereby preventing slippage of the looper thread. That is, a seam ravel can surely be prevented in its developmental stage.

Further in the present invention, the needle plate base attached to the sewing machine bed is divided into the two sections: the right needle plate base for attaching the needle plate thereto and swingably supporting the thread hanging hook of the needle thread holding mechanism; and the right needle plate base for fixedly supporting the stopper member of the stopper mechanism, the hook actuator, and the stopper actuator. Hence, as compared with handling of the single long and large needle plate as in the case of the technique described in the already-filed patent application by the present applicant, the attachment (installation) of the entirety of the ravel preventing apparatus with respect to the sewing machine bed can be easily carried out with less effort because the left and right needle plate bases can be individually attached to the sewing machine bed, and the ravel preventing apparatus can be incorporated into the sewing machine bed.

Furthermore, if after the seam ravel preventing apparatus is incorporated into the sewing machine bed, it becomes necessary to adjust stitch performation by correcting the position and motion loci of components for carrying out the sewing action which are stored below the needle plate base and inside the sewing machine bed, such as the looper and the members for actuating the looper, or it becomes necessary to perform maintenance, such as mending and replacement, on various types of components stored below the needle plate base and inside the sewing machine bed, it is unnecessary to remove the right needle plate base for fixedly supporting the hook actuator and the stopper actuator to which an air tube or an electric power supply line is connected, and a sufficiently wide operating space can be ensured by unfastening and removing only the left needle plate base from the sewing machine bed.

Hence, the adjustment of sewing performation, and the maintenance such as the mending and replacement on the various types of components stored inside the sewing machine bed can be performed extremely easily, simply, and efficiently only by handling the small and lightweight left needle plate base to which neither the air tube nor the electric power supply line clings. This produces the effect that satisfactory sewing performation and the predetermined ravel prevention function can constantly be exhibited with superior reproducibility, thereby succeeding in solving the problem remained unsolved in the already-filed patent application by the present applicant.

In the multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to the present invention, the stopper mechanism is preferably made up of a stopper member which is directly connected to the hook actuator and moves linearly reciprocally; a swing lever engageable with and disengageable from a part of the stopper member; a spring for swingingly energizes the swing lever in a direction in which the thread hanging hook is positioned at the standby position; and the stopper actuator for disengaging the swing lever from the part of the stopper member against an energizing force of the spring.

In this case, the action of the stopper member in a return direction (the action in a direction in which the thread hanging hook is positioned at the standby position) is performed by the energizing force of the spring. Therefore, the stopper actuator for actuating the swing lever that engages with or disengages from the part of the stopper member may be one capable of pushingly driving the stopper member. Hence, the use of an air cylinder as the stopper actuator allows for employment of a single acting type air cylinder, thereby achieving downsizing and cost reduction of the stopper actuator.

In the multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to the present invention, the swing lever in the stopper mechanism is preferably attached to a movable base attached laterally position-adjustably to the right needle plate base.

In this case, by the lateral position adjustment of the movable base with respect to the right needle plate base, the timing that the looper comes out of the needle thread loop held by the thread hanging hook can easily and appropriately be adjusted attached to ensure self-looping for seam ravel prevention.

In the multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to the present invention, the hook actuator of the needle thread holding mechanism and the stopper actuator of the stopper mechanism are preferably fixedly supported on a lower surface of the right needle plate base in a vertical two-stage fashion.

In this case, the two actuators are fixedly supported on the right needle plate base in the vertical two-stage fashion, and therefore the planar space occupied by these two actuators can be reduced to permit compactness, thereby allowing them to be nicely stored inside the sewing machine bed, compared with the case where the two actuators are disposed at the positions separated from each other (side-by-side arrangement) as in the case of the technique described in the already-filed patent application by the present applicant.

In the multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to the present invention, the thread hanging hook of the needle thread holding mechanism is preferably provided with a looper thread holder which holds the looper thread extending from the looper to the fabric at a more forward position than the drop position of the needle by swinging together with the thread hanging hook of the needle thread holding mechanism around the support shaft in the plane substantially parallel to the needle plate between the thread hooking position, the hold position, and the standby position.

In this case, the looper thread is held at a position ahead of the drop position of the needle by the looper thread holder that cooperates with the thread hanging hook. This simple structure allows the looper thread to be surely positioned together with the needle thread. Accordingly, the self-looping can be surely performed to more surely prevent the seam ravel.

In the multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to the present invention, the looper thread holder is preferably attached position adjustably to the thread hanging hook.

In this case, a relative position between the needle thread and the looper thread can be appropriately set, and the self-looping can be performed more surely to further enhance the seam ravel prevention effect.

In the multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to the present invention, the hook actuator of the needle thread holding mechanism and the stopper actuator of the stopper mechanism are preferably both air cylinders.

In this case, the thread hanging hook in the needle thread holding mechanism and the swing lever in the stopper mechanism can be operated with superior response on the basis of a control signal from the control section, thereby achieving the reliable and efficient seam ravel prevention effect after the normal sewing.

As these actuators, electromagnetic solenoids or the like may be used.

In the multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to the present invention, a pin is preferably protruded upward from a connection end portion of the connecting member, and a connection end portion of the thread hanging hook is preferably provided with a connecting hole that is insertable into the pin from above the pin, and is drawable in an upward direction.

In this case, when the left needle plate base is removed from the sewing machine bed in an upward direction by unfastening it from the upper surface of the sewing machine bed in order to perform the maintenance, such as mending and replacement, on the various types of components stored inside the sewing machine bed, the connection between the thread hanging hook and the connecting member can be released only by raising the left needle plate base, without requiring any troublesome operation, such as unfastening and removing a screw that connects the connecting member and the thread hanging hook, or pulling-out of a connecting pin. Additionally, after the adjustment and maintenance, the thread hanging hook and the connecting member can be returned to the predetermined connected state only by fixedly fastening the left needle plate base to the sewing machine bed from above. This further saves time and trouble during the adjustment and maintenance.

In the multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to the present invention, the left needle plate base or the sewing machine bed are preferably provided with protruding knock pins which are capable of positioning the left needle plate base to the sewing machine bed at a plurality of positions away from a plurality of fixedly connecting portions and connection release portions by means of the screw members, and the sewing machine bed or the left needle plate base is preferably provided with pin holes engageable with the knock pins.

In this case, when the left needle plate base is attached to and detached from the sewing machine bed, the left needle plate base can be surely positioned at a predetermined position in the sewing machine bed by the engagement between the plurality of knock pins and pin holes. Therefore, even when the left needle plate base is repetitively attached to and detached from the sewing machine bed every time the adjustment and maintenance are carried out, the left needle plate base can be attached to the sewing machine bed by constantly ensuring predetermined position and posture. Consequently, besides the normal sewing, the seam ravel prevention function can also be constantly performed appropriately surely.

The seam ravel preventing apparatus of the present invention is suitably applicable to a horizontal tube type multi-thread chain stitch sewing machine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a general appearance of a horizontal tube type multi-thread chain stitch sewing machine with a seam ravel preventing apparatus according to an embodiment of the present invention;

FIG. 2 is a perspective view showing the structure of the main parts of the seam ravel preventing apparatus in the horizontal tube type multi-thread chain stitch sewing machine;

FIG. 3 is a perspective view showing a state in which a part of the structure of the main parts of the seam ravel preventing apparatus is removed;

FIG. 4 is a plan view showing the structure of the main parts of the seam ravel preventing apparatus;

FIG. 5 is a bottom plan view of the main parts for explaining the structure of a stopper mechanism and a first action thereof in the seam ravel preventing apparatus;

FIG. 6 is a bottom plan view for explaining the structure of the stopper mechanism and a second action thereof;

FIG. 7 is a bottom plan view for explaining the structure of the stopper mechanism and a third action thereof;

FIG. 8 is a bottom plan view for explaining the structure of the stopper mechanism and a fourth action thereof;

FIG. 9 is a block diagram showing the configuration of a control system of the horizontal tube type multi-thread chain stitch sewing machine including the seam ravel preventing apparatus;

FIG. 10 is a time chart for explaining operation contents of a control section in the seam ravel preventing apparatus;

FIG. 11 is an explanatory drawing of a first ravel prevention action by the seam ravel preventing apparatus;

FIG. 12 is an explanatory drawing of a second ravel prevention action by the seam ravel preventing apparatus;

FIG. 13 is an explanatory drawing of a third ravel prevention action by the seam ravel preventing apparatus;

FIG. 14 is an explanatory drawing of a fourth ravel prevention action by the seam ravel preventing apparatus;

FIG. 15 is an explanatory drawing of a fifth ravel prevention action by the seam ravel preventing apparatus;

FIG. 16 is an explanatory drawing of a sixth ravel prevention action by the seam ravel preventing apparatus;

FIG. 17 is an explanatory drawing of a seventh ravel prevention action by the seam ravel preventing apparatus;

FIG. 18 is a view of a seam structure of twin-needle multi-thread chain stitch obtained by the present invention, viewed from the rear surface of a fabric;

FIG. 19 is an explanatory drawing of ravel prevention effect of the seam structure shown in FIG. 18;

FIG. 20 is a view of a general seam structure in a portion at the end of sewing, viewed from the rear surface of the fabric;

FIG. 21 is a plan view roughly showing the structure of the main parts of the seam ravel preventing apparatus of the technique described in the already-filed patent application by the present applicant;

FIG. 22 is a bottom plan view roughly showing the structure of the main parts of the seam ravel preventing apparatus of the technique described in the already-filed patent application by the present applicant; and

FIG. 23 is a plan view for explaining action states of the main parts of the seam ravel preventing apparatus of the technique described in the already-filed patent application by the present applicant.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

An embodiment of the present invention is described below with reference to the accompanying drawings.

FIG. 1 is the perspective view showing the general appearance of the horizontal tube type multi-thread chain stitch sewing machine according to the embodiment of the present invention. FIGS. 2 and 3 are the perspective views showing the structure of the main parts of the seam ravel preventing apparatus included in the horizontal tube type multi-thread chain stitch sewing machine according to the present invention. FIG. 4 is the plan view showing the structure of the main parts of the seam ravel preventing apparatus. The following description is made using terms “left,” “right,” “forward,” and “backward” indicated by arrows in FIGS. 2 to 4. That is, the term “forward” denotes the side near a sewing operator. The term “backward” denotes the side away from the sewing operator. The terms “left” and “right” denote the left and right, viewed from the front near the sewing operator.

In the present embodiment, structural members and structural portions, which are identical to or corresponding to the technique of the already-filed patent application by the present applicant described with reference to FIGS. 21 to 23, are described using the same reference numerals.

As shown in FIG. 1, in the horizontal tube type multi-thread chain stitch sewing machine according to the present embodiment of the present invention, a sewing machine arm C and a sewing machine bed B are extended substantially horizontally toward the left from an upper position and a lower position of a body section D, respectively. As shown in FIG. 4, the horizontal tube type multi-thread chain stitch sewing machine includes a looper 1, two needles 2 and 2 (refer to FIGS. 11 to 17), a needle plate base 11 secured to an upper surface of the sewing machine bed B, a seam ravel preventing apparatus H incorporated into the needle plate base 11, and a needle plate P secured onto the needle plate base 11. The needles 2 and 2 move up and down via actions of a needle bar driving mechanism. Alphabetic characters A and A in FIGS. 2 and 4 denote needle drop positions (descent positions) of the needles 2 and 2, respectively. The needle drop positions A and A are set with a distance laterally interposed therebetween at a substantially middle portion of the needle plate P.

The looper 1 moves forward and backward (left forward motion and right backward motion) via the actions of the looper driving mechanism. A solid line in FIG. 4 indicates a state in which the looper 1 has moved to a left forward position, and a broken line in FIG. 4 indicates a state in which the looper 1 has moved to a right backward position. As shown by the solid line in FIG. 4, a front end portion of the looper 1 at the left forward position extends leftward across the needle drop positions A and A. As shown by the broken line in FIG. 4, the front end portion of the looper 1 at the right backward position is located rightward away from the needle drop positions A and A.

The horizontal multi-thread chain stitch sewing machine sews a fabric (not shown) set on the needle plate P by the up and down movements of the needles 2 and 2, and the left forward and right backward movements of the looper 1. The fabric is pressed against the needle plate P by a presser foot (not shown), and is fed in a direction of arrow Y in FIG. 4 by the action of a feed mechanism installed inside a sewing machine bed B. The feed mechanism includes a feed dog that repeats the following movements in which the feed dog moves in a backward direction while protruding from the needle plate P, and moves in a forward direction while sinking under the needle plate P. The fabric is intermittently fed in a direction of arrow Y by the feed dog.

The foregoing needle bar driving mechanism, looper driving mechanism, and feed mechanism are well known mechanisms which operate mutually synchronously by power transmission from a sewing machine spindle (not shown). The needles 2 and 2 respectively hold needle threads 20 and 20 (refer to FIGS. 11 to 17), and pass through the fabric and reach below the needle plate P during discontinuation of the fabric feeding, and thereafter, these needles move up and pass through the fabric in an upward direction. The looper 1 holds a looper thread 10 (refer to FIGS. 11 to 17), and moves toward the left at the same moment that the needles 2 and 2 start moving up, thereby catching loops 20 a and 20 b of the needle threads 20 and 20 which are formed below the needle plate P. The fabric is fed when the needles 2 and 2 move up. The needle 2 and 2 move down while passing through the fed fabric, and catch the looper thread 10 held by the looper 1 retracted toward the right. The multi-thread chain stitch sewing machine forms multi-thread chain stitch seams on the fabric by repeating the forgoing actions.

The seam ravel preventing apparatus H included in the foregoing horizontal tube type multi-thread chain stitch sewing machine includes a needle thread holding mechanism, a stopper mechanism, a connecting rod 35 as a connecting member for interlockingly connecting a thread hanging hook 3 (described later) of the needle thread holding mechanism and a stopper member 4 (described later) of the stopper mechanism, and a control section 8 (described later).

The needle thread holding mechanism includes the thread hanging hook 3, and a reciprocating type thread handling cylinder 32 as a hook actuator for drivingly swinging the thread hanging hook 3 around a vertical extending support shaft 30 between a standby position away from the looper 1 and a thread hooking position adjacent to the looper 1. The supporting shaft 30 as the swing center of the thread hanging hook 3 is disposed in the vicinity of a right back side corner of the needle plate P, and is supported on the needle plate base 11.

The thread hanging hook 3 has an arcuately curved shape, and is continuously formed so as to be folded forward at a front end portion of a support arm 3 e extending leftward from the support shaft 30. A front end portion of the thread hanging hook 3 is faced onto the needle drop positions A and A from the left back on a lower side of the needle plate P. An outward protruding hook portion 3 b is formed at the front end portion of the thread hanging hook 3. The support arm 3 e has an extended portion 3 c extending forward from the support shaft 30, and one end of the connecting rod 35 is connected to a front end portion of the extended portion 3 c.

As shown in FIG. 4, a looper thread holder 6 having an arcuately curved shape is fastened together with a base part of the thread hanging hook 3 via two fixing screws 60 and 60. A front end portion of the looper thread holder 6 extends forward substantially along the left side of the thread hanging hook 3, and is faced onto the needle drop positions A and A at a front position of the front end portion of the thread hanging hook 3. A looper thread receiving portion 6 a branched into two is formed at the front end portion of the looper thread holder 6. The looper thread holder 6 permits position adjustment with respect to the thread hanging hook 3 by unfastening the fixing screws 60 and 60. The position adjustment ensures holding of the looper thread 10 by the looper thread receiving portion 6 a located at the front end.

As shown in FIGS. 5 to 8, the stopper mechanism is comprised of a stopper member 4 which is fastened to a front end portion (left end portion) of an output rod 31 of the thread handling cylinder 32 via a fixing screw 36, and is linearly reciprocally drivingly moved in a lateral direction due to expansion and contraction of the thread handling cylinder 32 by operating air supplied via an air tube 33; a swing lever 9 engageable with and disengageable from a part of the stopper member 4; a spring 91 which allows the swing lever 9 to be engaged with the part of the stopper member 4, and swingingly energizes in a direction in which the thread hanging hook 3 is located at the standby position; and a stopper cylinder 42 of single acting type (drivingly push-out type in the left direction) as a stopper actuator which forcibly disengages the swing lever 9 from the part of the stopper member 4 against the swing energizing force of the spring 91.

The output rod 41 of the stopper cylinder 42 is configured to swing the swing lever 9 counterclockwise against the swing energizing force of the spring 91 as the stopper cylinder 42 is drivingly pushed out toward the left by the operating air supplied via the air tube 43.

The swing lever 9 is supported on the upper surface of a swing lever mount (movable mount) 92 so as to be swingable around the center of the vertically extending support shaft 90. The swing lever 9 has at a front end portion thereof an engaging claw 9 a engageable with the part of the stopper member 4. As shown in FIG. 5, the swing lever 9 is contacted with a side part of the stopper member 4 by the energizing force of the spring 91 during the time the stopper member 4 is drivingly moved toward the left by the expansion stroke of the thread handling cylinder 32, that is, during the time the thread hanging hook 3 is moved to the standby position. As shown in FIG. 6, the swing lever 9 swings clockwise around the support shaft 90 by the energizing force of the spring 91, and the engaging claw 9 a at the front end thereof enters a state of being engageable with the part of the stopper member 4 while the stopper member 4 is drivingly moved toward the right by the contraction stroke of the thread handling cylinder 32.

As shown in FIG. 7, by allowing the contracted thread handling cylinder 32 to resume somewhat the contraction stroke, the engaging claw 9 a at the front end of the swing lever 9 engages with the part of the stopper member 4, thereby temporarily suspending the leftward driving movement of the stopper member 4. In the state in which the stopper member 4 is thus temporarily suspended, the thread hanging hook 3 moves to the hold position between the standby position and the thread hooking position, and remains there via the connecting rod 35. At this time, the hook portion 3 b at the front end of the thread hanging hook 3 moves from the thread hooking position shown in FIG. 4 (between the right and left needle drop positions A and A) to left back of the left needle drop position A, and hooks the left needle thread 20 and holds it at the hold position. The looper thread holder 6 moves forward to the front of the looper 1, and the looper thread receiving portion 6 a at the front end thereof holds the looper thread 10 at a more forward position than the left needle drop position A.

Further, as shown in FIG. 8, the swing lever 9 is swung counterclockwise against the swing energizing force of the spring 91 by allowing the output rod 41 to be drivingly pushed out toward the left as the stopper cylinder 42 expands. This swing allows the engaging claw 9 a at the front end of the swing lever 9 to be disengaged from the part of the stopper member 4, thereby releasing the temporary suspension of the stopper member 4. Consequently, the thread handling cylinder 32 is subjected to a maximum expansion stroke, and the thread hanging hook 3 and the looper thread holder 6 are swingingly returned to the standby position via the connecting rod 35.

As described above, in the present embodiment, the thread hanging hook 3 and the looper thread holder 6 of the needle thread holding mechanism swing into the standby position, the thread hooking position, and the hold position by the expansion and contraction strokes of the thread handling cylinder 32 and the stopper cylinder 42.

The horizontal tube type multi-thread chain stitch sewing machine in the present embodiment further includes a thread cutting mechanism 5 for cutting the needle threads 20 and the looper thread 10 after a sewing action is terminated. As shown in FIGS. 16 and 17, the thread cutting mechanism 5 includes a thread cutting hook 50, a thread cutting knife 51, a leaf spring 59 for pressing the thread cutting hook 50 against a sliding contact part between itself and the thread cutting knife 51, and a thread cutting actuator 58 (refer to FIG. 9). The thread cutting hook 50 has at a front end portion thereof a first hook part 51 and a second hook part 53 which are protruding backward. The thread cutting mechanism 5 is well known, and therefore, description and illustration of other detailed structures are omitted here.

FIG. 9 is the block diagram showing the configuration of the control system of the horizontal tube type multi-thread chain stitch sewing machine including the seam ravel preventing apparatus H as described above. A pedal depresson signal 21 a and a pedal back signal 21 b generated by a pedal switch 21, a needle position signal 22 generated when the needles 2 and 2 are in the vicinity of a top dead center, a thread cut signal 23, and a needle thread wipe signal 24 are respectively inputted to the control section 8 of the multi-thread chain stitch sewing machine.

On the other hand, the control section 8 outputs action control signals to the thread handling cylinder 32, the stopper cylinder 42, and the thread cutting actuator 58, respectively. The thread hanging hook 3 and the looper thread holder 6 act as previously described according to the action control signals outputted from the control section 8 to the thread handling cylinder 32 and the stopper cylinder 42, and the thread cutting actuator 58 of the thread cutting mechanism (not shown) expands and contracts according to the thread cut signal 23 outputted from the control section 8.

The control section 8 also outputs action control signals respectively to a sewing machine motor 80 as a driving source of the sewing machine spindle, a presser foot cylinder 81 for moving up and down a presser foot for pressing the fabric, an air wiper 82 for wiping up the needle threads 20 and 20 to be cut as described later, a feed reducing mechanism 83 for adjusting a fabric feeding rate, and a looper thread restraining mechanism 84 for restraining the feed of the looper thread 10 to the looper 1.

The feed reducing mechanism 83 reduces the fabric feed rate by changing a mode of operation of the feed dog in the feed mechanism. For example, time period during which the feed dog acts on the fabric on the needle plate P is reduced by inclining an action passage of the feed dog with respect to the needle plate P so as to reduce time period during which it protrudes upward from the needle plate P, or a unit feed pitch by the feed dog is reduced by changing a length of a lever for cyclically operating the feed dog. The feed reducing mechanism 83 of this type is well known, and therefore detailed illustration and description thereof are omitted here.

The looper thread restraining mechanism 84 includes a thread tension disc for squeezing a mid-portion of the looper thread 10 to be fed to the looper 1, and an actuator that operates to increase or decrease strength to squeeze the looper thread by the thread tension disc. The strength to squeeze the looper thread by the thread tension disc is enhanced to increase resistance applied to the looper thread 10, thereby restraining the feed of the looper thread 10. The looper thread restraining mechanism 84 of this type is well known, and therefore detailed illustration and description thereof are omitted here.

At the end of the sewing for forming the multi-thread chain stitch seams, the control section 8 executes a seam ravel prevention operation in the multi-thread chain stitch seams by allowing the thread hanging hook 3 and the looper thread holder 6 to act in association with the sewing machine motor 80, the presser foot cylinder 81, the air wiper 82, the feed reducing mechanism 83, and the looper thread restraining mechanism 84.

FIG. 10 is the time chart showing time series operation contents of the control section 8 for the purpose of ravel prevention. The control section 8 is a computer including a CPU, a ROM, and a RAM. The ravel prevention operation according to the time chart shown in FIG. 10 is executed by a series of operations of the CPU according to a control program stored in the ROM.

FIGS. 11 to 17 are the explanatory drawings of the ravel prevention operation by the ravel preventing apparatus H in the horizontal tube type multi-thread chain stitch sewing machine of the present invention, and show operation statuses of the thread hanging hook 3 and the looper thread holder 6, and the thread cutting hook generated by the operation of the control section 8 according to the time chart of FIG. 10.

When the sewing operator using the sewing machine terminates normal sewing, the operator suspends a depressing operation of a pedal for driving the sewing machine, and then performs the ravel prevention operation. In this case, the operator performs a pedal back operation of the pedal. The pedal switch 21, attached to the pedal, outputs the pedal depression signal 21 a during the pedal depression operation, and outputs the pedal back signal 21 b in response to the pedal back operation.

When the normal sewing is terminated, and the pedal for driving the sewing machine is returned from a depressed state to a neutral state at time S1 in FIG. 10, namely, when neither the pedal depression signal 21 a nor the pedal back signal 21 b is outputted from the pedal switch 21, the control section 8 outputs a suspension command to the sewing machine motor 80 by referring to the needle position signal given to the input side. Consequently, the sewing machine is temporarily suspended in a state in which the needles 2 and 2 are positioned in the vicinity of the top dead points and the looper 1 has moved toward the left.

Thereafter, the control section 8 stands by until the pedal is subjected to the pedal back operation. When the pedal back operation is performed, and the pedal back signal 21 b is inputted to the input side at time S2 in FIG. 10, the control section 8 starts the ravel prevention operation as described below. When the pedal depression signal 21 a is inputted again from the pedal switch 21, the control section 8 returns to the normal sewing action. Therefore, the sewing operator can continue the normal sewing by performing the pedal depressing operation again.

In FIG. 10, though the neutral state is maintained during a period of time between S1 and S2, maintaining the neutral state is not necessarily required. The pedal operation at the end of the normal sewing may be continuously shifted from the pedal depression state to the pedal back state. In this case, when passing through the neutral position in the shift progress, it enters a non-signal state in which neither the pedal depression signal 21 a nor the pedal back signal 21 b is outputted. Using the non-signal state as a trigger, the control section 8 starts the ravel prevention operation after achieving the state in which the needles 2 and 2 are raised to near the top dead points and the looper 1 is moved toward the left, as described above.

Also in the time chart of FIG. 10, though the pedal back operation at time S2 is continued during execution of the ravel prevention operation described later, it is unnecessary to continue the pedal back operation until the ravel prevention operation is terminated, and the ravel prevention operation is continuously executed by the operation of the control section 8 even after the input of the pedal back signal 21 b is suspended.

FIG. 11 shows the states of the needles 2 and 2 and the looper 1 at the start of the ravel prevention operation. The needles 2 and 2 have passed through and are now located above the fabric on which multi-thread chain stitch seams M are formed by the two needle threads 20 and 20 and the looper thread 10. The looper 1 has moved toward the left below the fabric, and is in a state of catching the needle thread loops 20 a and 20 a respectively formed by the needles 2 and 2. When the needle threads 20 and 20 and the looper thread 10 are cut in this state, the portion at the end of sewing as shown in FIG. 20 is formed.

After starting the ravel prevention operation, the control section 8 firstly provides an operation command to the thread handling cylinder 32 on the output side. In response to this command, the thread handling cylinder 32 moves from a state of expansion shown in FIG. 5 to a state of contraction shown in FIG. 6, and the stopper member 4 is drivingly moved toward the right. Accordingly, the thread hanging hook 3 and the looper thread holder 6 move from the standby position to the thread hooking position by swinging around the support shaft 30 via the stopper member 4 and the connecting rod 35. At this time, the hook portion 3 b at the front end of the thread hanging hook 3 hooks the needle thread loop 20 a on one side (left side), and the swing lever 9 in the stopper mechanism swings clockwise around the support shaft 90 by the energizing force of the spring 91, and the engaging claw 9 a at the front end thereof enters the state of being engageable with the part of the stopper member 4.

Immediately thereafter, the control section 8 provides an operation command to the thread handling cylinder 32. Under the operation command, the thread handling cylinder 32 expands somewhat from the state shown in FIG. 6 to the state shown in FIG. 7, and the stopper member 4 is linearly drivingly moved toward the left. During the slight expansion of the thread handling cylinder 32, the engaging claw 9 a at the front end of the swing lever 9 engages with the part of the stopper member 4, thereby temporarily suspending a leftward driving movement of the stopper member 4. In the state in which the leftward driving movement of the stopper member 4 is temporarily suspended, as shown in FIG. 12, the thread hanging hook 3 moves via the connecting rod 35 to the hold position between the standby position and thread hooking position, and remains there and holds the left needle thread loop 20 a at the hold position. The looper thread holder 6 moves toward the front of the looper 1, and the looper thread receiving part 6 a at the front end thereof holds the looper thread 10 at a more forward position than the left needle drop position A.

After the thread hanging hook 3 and the looper thread holder 6 are thus moved to and remain at the hold position, the control section 8 provides operation commands respectively to the sewing machine motor 80, the feed-reducing mechanism 83, and the looper thread restraining mechanism 84 at time S3 in FIG. 10. These operation commands are provided by referring to the needle position signal 22 in a period of time during which the needles 2 and 2 move down and move up again to the positions near the top dead points. Accordingly, the sewing action for one stich on the fabric is carried out. The sewing for the one stitch is carried out at a lower feed rate than during the normal sewing by the action of the feed-reducing mechanism 83. The sewing for the one stitch is also carried out by the action of the looper thread restricting mechanism 84 in a state in which the feed of the looper thread 10 to the looper 1 is restrained. This improves tightness of the looper thread 10 at the end of the sewing, thereby enhancing the ravel prevention effect described later.

As shown in FIG. 12, the thread hanging hook 3 and the looper thread holder 6 continue the holding of the needle thread 20 and the looper thread 10 until the fabric feed is completed, and the needles 2 and 2 pass through the fabric and move down, and the left needle 2 passes through the needle thread loop 20 a held by the thread hanging hook 3 and catches the needle thread loop 20 a. At this time, the looper thread 10 held by the looper thread holder 6 is located across the front of the left needle 2, as shown in FIG. 12. Hence, the left needle 2 does not catch the looper thread 10, and the looper thread 10 is merely caught behind the looper 2 by the right needle 2.

At the time the left needle 2 catches the needle thread loop 20 a, namely, at time S4 in FIG. 10, the control section 8 allows the stopper cylinder 42 of the stopper mechanism to expand by providing an operation command to the stopper cylinder 42. Accordingly, the output rod 41 is drivingly pushed out toward the left. Consequently, as shown in FIG. 8, the swing lever 9 is swung counterclockwise against the swing energizing force of the spring 91, and the engaging claw 9 a at the front end of the swing lever 9 is disengaged from the part of the stopper member 4, thus allowing for a release of the temporary suspension of the stopper member 4. Upon the release of the temporary suspension of the stopper member 4, the thread handling cylinder 32 is expanded to its maximum at time S4. Consequently, as shown in FIG. 13, the thread hanging hook 3 and the looper thread holder 6 performs a return movement from the hold position to the standby position by swinging around the support shaft 30 via the stopper member 4 and the connecting rod 35, and then releases the holding of the needle thread loop 20 a and the looper thread 10.

The looper 1 then performs a right retraction action as the needles 2 and 2 move down, and slips out of the caught needle thread loop 20 a. Upon the slipping-out of the looper 1, as shown in FIG. 14, the right needle 2 enters a state of catching the looper thread 10 similarly during the normal sewing, whereas the left needle 2 enters a state of catching the left needle thread loop 20 a.

In this state, the looper 1 converts to a left forward movement, and the needles 2 and 2 convert to an upward movement. As shown in FIG. 15, the looper 1 that performs the left forward movement catches the left and right needle thread loops 20 a and 20 b, and the needles 2 and 2 that move up pass through the fabric in the upward direction. Accordingly, the needle thread 20 caught by the looper 1 interloops the looper thread at the position of the right needle 2, whereas the needle thread 20 performs so-called selflooping, that is, looping the previously formed needle thread loop 20 a with the needle thread 20 at the position of the left needle 2.

After the sewing action for the one stitch, it is finished in a state in which the needles 2 and 2 move up to the vicinity of the top dead points, and the looper 1 reaches the vicinity of the end of the leftward movement. Thereafter, the control section 8 stands by until a thread cut signal 23 is applied thereto. Upon receipt of the thread cut signal 23 at time S5 in FIG. 10, the control section 8 allows the thread cutting actuator 58 of the thread cutting mechanism to perform a predetermined operation by providing an operation command to the thread cutting actuator 58. Accordingly, the thread hanging hook 50 reaches a forward movement end along the upper part of the looper 1, as shown in FIG. 16. At this time, the first hook part 52 at the front end of the thread cutting hook 50 passes through the needle thread loops 20 a and 20 b held by the looper 1 to the left side of the looper thread 10 extending from the front end of the looper 1 to the fabric, and the second hook part 53 is opposed to the left needle thread 20 from the left side thereof.

Subsequently, the thread cutting hook 50 located at the forward movement end performs a right backward movement. At this time, the first hook part 52 catches the looper thread 10, and the second hook part 53 successively catches the two needle threads 20 and 20. The looper thread 10 and the needle threads 20 and 20 caught in this manner are then pulled to a retraction end of the thread cutting hook 50, and are cut by being brought into sliding contact with an edge portion at the front end of the thread cutting knife 51, as shown in FIG. 17. An end portion of the cut looper thread 10 is held in sandwich fashion between the thread cutting hook 50 and the leaf spring 59 at a position closer to the looper 1 than a cutting position.

The looper thread restraining mechanism 84 continues to operate and applies a predetermined tensile force to the looper thread 10 extending from the front end of the looper 1 to the fabric, until the foregoing thread cutting operation is terminated. This ensures that the first hook part 52 at the front end of the thread cutting hook 50 catches and cuts the non-loose looper thread 10.

After the foregoing cutting operation, the control section 8 stands by until a needle thread wipe signal 24 is inputted thereto. When the needle thread wipe signal 24 is inputted thereto at time S6 in FIG. 10, the control section 8 allows the air wiper 82 to operate by outputting an operation command to the air wiper 82. The air wiper 82 blows out air and blows up cut end portions of the needle threads 20 and 20 that are continuous with the needles 2 and 2. Thereafter, the control section 8 allows the presser foot cylinder 81 to act to raise the presser foot for pressing the fabric by outputting an operation command to the presser foot cylinder 81 at time S7 in FIG. 10, thereby terminating the sequence of the ravel prevention operation.

The foregoing sequence of the ravel prevention operation produces the multi-thread chain stitch seams M by the horizontal tube type multi-thread chain stitch sewing machine, as shown in FIG. 18. Referring to FIG. 18, the looper thread 10 is passed through the inside of the right needle thread loop 20 a (the left in FIG. 18 in which the seams M are viewed from the rear surface of the fabric) which is finally formed in the multi-thread chain stitch seams M on the rear surface of the fabric, and is turned back in front of the right needle thread 20 that goes through the rear surface of the fabric during the sewing action for one stitch for the purpose of the ravel prevention, and is then cut at a certain position after being passed through again the inside of the right final needle thread loop 20 a.

On the other hand, the left (the right in FIG. 18) needle thread 20 that goes through the rear surface of the fabric during the sewing action for the one stitch for the ravel prevention passes through the left needle thread loop 20 b finally formed on the rear surface of the fabric during the normal sewing, and forms a chain stitch seam by selflooping the left final needle thread loop 20 b, as previously described. Therefore, as shown in FIG. 18, the looper thread 10 enters a state of being pressed between the left needle thread 20 and the left final needle thread loop 20 b.

In FIG. 18, the left final needle thread loop 20 b is illustrated in a loose state in order to clarify entanglement with the needle thread 20. However, as shown in FIG. 19, the actual left final needle thread loop 20 b is strongly tightened after the needle thread 20 passes therethrough, and enters the same state as the right final needle thread loop 20 a. Then, when the cut end portion of the looper thread 10 is pulled in the arrowed direction as shown in FIG. 19, the loop of the looper thread 10 passing through in front of the right needle thread 20 is contracted and pulled into the right final needle thread loop 20 a. As a result, the needle thread 20 enters a state of being held between the looper thread 10 and the right final needle thread loop 20 a, and the needle thread 20 and the looper thread 10 make a knot as shown in FIG. 19. This knot also applies resistance to the looper thread 10, and performs the function of preventing slipping-out of the looper thread 10. Accordingly, in the state as shown in FIG. 19, the left selflooping portion and the right knot cooperate to surely prevent the ravel of the multi-thread chain stitch seams M.

The characteristic features of the multi-thread chain stitch sewing machine with the seam ravel preventing apparatus having the foregoing structure and ravel prevention operation as described in detail above, namely, the improved structure employed in the present invention in order to solve the problem remained unsolved in the already-filed patent application of the present applicant is described below by focusing on FIGS. 2 to 4.

As shown in FIGS. 2 to 4, the needle plate base 11 attached to the upper surface of the sewing machine bed B is divided into a left needle plate base 11L and a right needle plate base 11R. The left needle plate base 11L has the needle plate P detachably attached to the upper surface thereof via a set screw 100, and supports the support shaft 30 as the center of swing of the thread hanging hook 3 of the needle thread holding mechanism.

Screw holes 101 are formed at a plurality of front and rear portions (two portions) in the vicinity of the left end part in the left needle plate base 11L, specifically, at portions away from the attachment position of the needle plate P in the vicinity of the front end (left end) of a sewing machine arm C indicated by a virtual line in FIG. 4. The left needle plate base 11L is attached to the upper surface of the sewing machine bed B so as to permit fastening and unfastening (attachment and detachment).

Further, as shown in FIG. 3, the upper surface of the sewing machine bed B and the left needle plate base 11L are provided with knock pins 103 and pin holes 104 into which the knock pins 103 fit, at positions away from two fastening positions via set screw members 102. The pin holes 104 are inserted into and engaged with the knock pins 103 from above, thereby positioning the left needle plate base 11L at predetermined position and posture with respect to the sewing machine bed B. In this state, the set screw members 102 are screwed into the screw holes 102, thereby allowing the left needle plate base 11L to be fastened against the upper surface of the sewing machine bed B.

Although the present embodiment describes and illustrates one in which the knock pins 103 protrude upward from the upper surface of the sewing machine bed B, and the pin holes 104 are formed in the left needle plate base 11L or, alternatively, the knock pins 103 may protrude downward from the lower surface of the left needle plate base 11L, and the pin holes 104 may be formed in the upper surface of the sewing machine bed B.

On the other hand, the right needle plate base 11R constitutes a cylinder attachment base for supporting the thread handling cylinder 32 and the stopper cylinder 42 (hereinafter the right needle plate base 11R is referred to as the cylinder attachment base). The foregoing stopper mechanism is disposed at a lower part of the cylinder attachment base 11R. To be specific, as shown in FIGS. 5 to 8, the thread handling cylinder 32 is fixedly supported on the lower surface of the cylinder attachment base 11R via an attachment screw 105. The stopper cylinder 42 is disposed below the thread handling cylinder 32 in a two-stage fashion, and the stopper cylinder 42 is fixedly supported on the cylinder attachment base 11R via an attachment screw 106.

The cylinder attachment base 11R is installed in a fixed state to a side surface of the sewing machine bed B via a set screw 107. The phrase “fixed state” denotes the state in which the ravel preventing apparatus H is fixed to a predetermined position by fastening the set screw member 107 when installing it into the sewing machine bed B, and is fixed at a predetermined installation position after the installation without performing any positional adjustment or the like.

One end (right end) portion of the connecting rod 35 is rotatably connected to the stopper member 4 in the stopper mechanism by a pin screw 108. In a certain part of the cylinder attachment base 11 R which corresponds to a connecting part between the one end of the connecting rod 35 and the stopper member 4 by the pin screw 108, a long groove 109 that is long in a lateral direction is formed so as to allow for a linear reciprocating movement of the stopper member 4 that linearly reciprocates in the lateral direction in response to the expansion and contraction of the thread handling cylinder 32.

A connection end portion 35 a of the other end of the connecting rod 35, which is connected to an extended part 3 c connected to the thread hanging hook 3, is bent downward in a depth corresponding to a substantial thickness of the extended part 3 c. A pin 110 is protruded upward from the connection end portion 35 a of the downward bent connecting rod 35. On the other hand, the extended part 3 c is provided with a connecting hole 111 that is insertable into the pin 110 from above the pin 110 and is drawable in an upward direction. This eliminates the need to perform an operation for fixedly connecting the connecting rod 35 and the extended part 3 c, for example, releasing an interlocking state between the two by unfastening a set screw or the like, when the left needle plate base 11L is removed from the sewing machine bed B by unfastening it from the sewing machine bed B. That is, the connecting hole 111 of the extended part 3 c can be drawn upward from the pin 110, and the interlocking state between the connecting rod 35 and the extended part 3 c (the thread hanging hook 3) can be released only by raising the left needle plate base 11L. Also, when attaching the left needle plate base 11L to the sewing machine bed B, only by an operation of shifting the left needle plate base 11L from above toward the sewing machine bed B, the connecting hole 111 is inserted into the pin 110 from above, thereby allowing the connecting rod 35 and the extended part 3 c (thread hanging hook 3) to return to the interlocking state. The connection end portion 35 a of the connecting rod 35 needs not necessarily be bent downward. That is, the connecting rod 35 may have a flat plate shape.

A swing lever attachment base (movable base) 92, which supports the swing lever 9 in the stopper mechanism so as to be swingable around the vertically extending support shaft 90, is attached to the cylinder attachment base 11R so as to permit lateral position adjustment via a long hole 93 being long in a lateral direction and a set screw 94. Accordingly, even after the cylinder attachment base 11R is installed in the fixed state into the sewing machine bed B via the screw member 107, timing the looper 1 slips out of the needle thread loop 20 a held by the thread hanging hook 3 can be optionally adjusted by performing the lateral position adjustment of the swing lever attachment base 92 with respect to the cylinder attachment base 11R. This ensures the selflooping for the seam ravel prevention.

In the horizontal tube type multi-thread chain stitch sewing machine with the seam ravel preventing apparatus H employing the structure having the foregoing characteristic features, when the seam ravel preventing apparatus H is installed into the sewing machine bed B, the left needle plate base 11L and the right cylinder attachment base 11R, which are obtained by dividing the needle plate base 11 into right and left sections, can be individually attached to the sewing machine bed B. Hence, as compared with handling of the single long and large needle plate as in the case of the technique described in the already-filed patent application by the present applicant, the attachment (installation) operation of the entirety of the ravel preventing apparatus H with respect to the sewing machine bed B can be easily carried out with less effort.

Additionally, if after the needle plate base 11 (the left needle plate base 11L and the right cylinder attachment base 11R) is installed into the sewing machine bed B, it becomes necessary to adjust stitch performation by correcting the position and motion loci of the components for performing sewing action which are located below the needle plate base 11 and are stored inside the sewing machine bed B, such as the looper 1 and actuating members therefor, or it becomes necessary to perform maintenance, such as mending and replacement, on various types of components stored below the needle plate base 11 and inside the sewing machine bed B, it is unnecessary to remove the cylinder attachment base 11R by which the thread handling cylinder 32 and the stopper cylinder 43 respectively having the air tubes 33 and 43 attached thereto are strongly supported during the installation thereof. A sufficiently wide operating space can be ensured only by unfastening and removing the left needle plate base 11L from the sewing machine bed B.

Hence, the adjustment of sewing performation, and the maintenance such as the mending and replacement on the various types of components stored inside the sewing machine bed B can be performed extremely easily, simply, and efficiently only by handling the small and lightweight left needle plate base 11L to which the air tubes 33 and 34 do not cling. Consequently, satisfactory sewing performation and the predetermined ravel prevention function can constantly be exhibited with superior reproducibility, thereby solving the problem remained unsolved in the already-filed patent application by the present applicant.

The present embodiment employs the structure in which the swing lever 9 in the stopper mechanism is swingingly energized by the spring 91 in the direction in which the thread hanging hook 3 in the needle thread holding mechanism is positioned at the standby position. Therefore, the action of the stopper member 4 in the return direction (the action in the direction in which the thread hanging hook is positioned at the standby position) is performed by the energizing force of the spring 9. This allows for employment of a single-acting type air cylinder as the stopper cylinder 42 for actuating the swing lever 9 that engages with or disengages from the part of the stopper member 4, thereby achieving downsizing and cost reduction of the stopper cylinder 42.

The present embodiment also employs the structure in which the thread handling cylinder 32 in the needle thread holding mechanism and the stopper cylinder 42 in the stopper mechanism are fixedly supported on the lower surface of the cylinder attachment base 11R in the vertical two-stage fashion. Therefore, the planar space occupied by the two air cylinders 32 and 42 can be reduced to permit compactness of the entirety of the ravel preventing apparatus H, thereby allowing the ravel preventing apparatus H to be nicely stored inside the sewing machine bed B, compared with the case where the two air cylinders 32 and 42 are disposed at the positions separated from each other (side-by-side arrangement) as in the case of the technique described in the already-filed patent application by the present applicant.

The present embodiment further employs the structure for attaching the looper thread holder 6 to the thread hanging hook 3 in the needle thread holding mechanism. The looper thread holder 6 holds the looper thread extending from the looper 1 to the fabric at a more forward position than the drop position of the needle 2 by swinging together with the thread hanging hook 3 in the plane substantially parallel to the needle plate P around the vertically extending support shaft 30 between the thread hooking position, the hold position, and the standby position. This simple structure can surely position the looper thread 10 together with the needle thread 20. Thereby, the selflooping can be surely performed to further ensure the seam ravel prevention effect.

Particularly, by position-adjustably attaching the looper thread holder 6 with respect to the thread hanging hook 3, the relative positions of the needle thread 20 and the looper thread 10 can appropriately be set, and the selflopping can be more surely performed to further enhance the seam ravel prevention effect.

The present embodiment further employs the structure in which the pin 110 is protruded upward from the connecting end portion 35 a of the connecting rod 35, and the connecting hole 111, which is insertable into the pin 110 from above the pin 110 and is upward drawable, is formed at the connecting end portion (extended part 3 c) closer to the thread hanging hook 3. Therefore, when the left needle plate base 11L is unfastened from the upper surface of the sewing machine bed B and is removed in an upward direction from the sewing machine bed B in order to perform the adjustment of stitch performation and the maintenance, such as the mending and replacement, on the various types of components stored inside the sewing machine bed B, the thread hanging hook 3 and the connecting rod 35 can be disengaged from each other only by raising the left needle plate base 11L, without requiring any troublesome operation, such as unfastening and removing the screw connecting the connecting rod 35 and the extended part 3 c closer to the thread hanging hook 3, or pulling-out of the connecting pin. Additionally, after the adjustment and maintenance, the thread hanging hook 3 and the connecting rod 35 can be returned to the predetermined connected state only by fastening the left needle plate base 11L to the sewing machine bed B from above. This further saves the labor in the adjustment and maintenance.

Although the foregoing embodiment has described the case of using the air cylinders as the hook actuator and the stopper actuator, electromagnetic solenoids may be used as these actuators.

Although the foregoing embodiment has also described the case of forming the multi-thread chain stitch seams by the two needles 20 and 20 and the single looper thread 10, it is applicable to one which forms multi-needle double chain stitch seams by using three or more needle threads, or one which forms one-needle chain stitch seams by using one needle thread, or a top-cover multi-thread chain stitch sewing machine which performs top cover sewing on multi-thread chain stitch seams.

The foregoing embodiment has also described the case of performing the ravel prevention in which one of the needle thread loops formed by the two needle threads 20 and 20 is caught and held at the hold position, and in this state, the sewing action for one stitch is performed for selflooping. Alternatively, a plurality of needle thread loops may be caught and held at the hold position, and the sewing action in the hold state may be for two switches or more without being limited to one stitch.

The foregoing embodiment has also described the case where the looper thread holder 6 the thread hanging hook of the needle thread holding mechanism is preferably provided with a looper thread holder which holds the looper thread extending from the looper to a fabric at a more forward position than the drop position of the needle by swinging together with the thread hanging hook around the support shaft in the plane substantially parallel to the needle plate between the thread hooking position, the hold position, and the standby position. Alternatively, the looper thread holder 6 and the thread hanging hook 3 may be disposed separately and be individually operated by a dedicated actuator different from the thread handling cylinder 32 for actuating the thread hanging hook 3. Further alternatively, it is not essential to install the looper thread holder 6.

INDUSTRIAL APPLICABILITY

The needle plate base is divided into the left and right sections, which are configured to be individually handled as the left needle plate base and the right cylinder attachment base. Hence, the attachment (installation) of the entirety of the ravel preventing apparatus to the sewing machine bed, and the adjustment of sewing performation, and the maintenance such as the mending and replacement on the various types of components stored inside the sewing machine bed can be performed easily with less labor, thus permitting a suitable application to the multi-thread chain stitch sewing machine.

What has been described above are preferred aspects of the present invention. It is of course not possible to describe every conceivable combination of components or methodologies for purposes of describing the present invention, but one of ordinary skill in the art will recognize that many further combinations and permutations of the present invention are possible. Accordingly, the present invention is intended to embrace all such alterations, combinations, modifications, and variations that fall within the spirit and scope of the appended claims. 

I claim:
 1. A multi-thread chain stitch sewing machine with a seam ravel preventing apparatus wherein the multi-thread chain stitch sewing machine comprises a needle having a drop position moving up and down while holding a needle thread; a looper which is movable forward and backward while holding a looper thread in a direction substantially orthogonal to a vertical movement path of the needle, and catches a needle thread loop formed below a needle plate by the needle during a forward movement; and a needle plate base having the needle plate attached thereto and being attached to an upper surface of a sewing machine bed, and wherein the multi-thread chain stitch sewing machine forms multi-thread chain stitch seams on a fabric by allowing the looper to catch the needle thread loop formed below the needle plate by the needle, and then by interlooping the needle thread with the looper thread held by the looper, the multi-thread chain stitch sewing machine with the seam ravel preventing apparatus comprising: a needle thread holding mechanism comprising (i) a thread hanging hook which is approachable and departable with respect to the looper, and swings around a vertically extending support shaft in a plane substantially parallel to the needle plate between a standby position away from the looper and a thread hooking position close to the looper, and (ii) a hook actuator for drivingly swinging the thread hanging hook to the standby position and the thread hooking position; a stopper mechanism comprising (iii) a stopper member disposed at a position farther away from the needle plate than the thread hanging hook of the needle thread holding mechanism, and permits temporary suspension and unsuspension of a swing of the thread hanging hook from the thread hooking position to the standby position so that the needle thread loop caught by the thread hanging hook at the thread hooking position is held at a hold position between the thread hooking position and the standby position, and (iv) a stopper actuator for performing the suspension and the unsuspension of the stopper member; a connecting member for interlockingly connecting the thread hanging hook of the needle thread holding mechanism and the stopper member of the stopper mechanism; and a control section for controlling the needle thread holding mechanism and the stopper mechanism in association with a vertical movement of the needle, forward and backward movements of the looper, and feed of the fabric, so that the looper is moved forward after a normal sewing is terminated, the thread hanging hook of the needle thread holding mechanism is brought near the looper, the needle thread loop caught at the thread hooking position is moved to the hold position, a resulting state is maintained until the needle descends through the needle thread loop caught by the looper, and thereafter, a sewing action for at least one stitch is performed, wherein the needle plate base is divided into two sections: a left needle plate base for attaching the needle plate thereto and supporting a swinging support shaft of the thread hanging hook; and a right needle plate base for fixedly supporting the stopper member and the hook actuator and the stopper actuator, and wherein the right needle plate base is fastened to the sewing machine bed, and the left needle plate base is fastenably and unfastenably fastened to an upper surface of the sewing machine bed via screw members.
 2. The multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to claim 1, further comprising: a feed reducing mechanism for feeding the fabric at a lower feed rate than during a normal sewing under an operation command provided from the control section, in the sewing action for the at least one stitch.
 3. The multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to claim 1, further comprising: a looper thread restraining mechanism for restraining feed of the looper thread to the looper under an operation command provided from the control section, after the looper thread is positioned ahead of or behind the drop position of the needle.
 4. The multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to claim 1, wherein the stopper mechanism comprises: the stopper member directly connected to the hook actuator and moves linearly reciprocally; a swing lever engageable with and disengageable from a part of the stopper member; a spring for swingingly energizes the swing lever in a direction in which the thread hanging hook is positioned at the standby position; and the stopper actuator for disengaging the swing lever from the part of the stopper member against an energizing force of the spring.
 5. The multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to claim 4, wherein the swing lever in the stopper mechanism is attached to a movable base attached laterally position-adjustably to the right needle plate base.
 6. The multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to claim 4, wherein the hook actuator of the needle thread holding mechanism and the stopper actuator of the stopper mechanism are fixedly supported on a lower surface of the right needle plate base in a vertical two-stage fashion.
 7. The multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to claim 1, further comprising: a looper thread holder which holds the looper thread extending from the looper to the fabric at a more forward position than the drop position of the needle by swinging together with the thread hanging hook of the needle thread holding mechanism around the support shaft in a plane substantially parallel to the needle plate, between the thread hooking position, the hold position, and the standby position; and an actuator for swinging the looper. thread holder.
 8. The multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to claim 1, wherein the looper thread holder is fastened together with the thread hanging hook of the needle thread holding mechanism to swing integrally with the thread hanging hook around the swinging support shaft in the plane substantially parallel to the needle plate, between the thread hooking position, the hold position, and the standby position.
 9. The multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to claim 8, wherein the looper thread holder is attached position adjustably to the thread hanging hook.
 10. The multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to claim 1, wherein the hook actuator of the needle thread holding mechanism and the stopper actuator of the stopper mechanism are both air cylinders.
 11. The multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to claim 1, further comprising a pin protruding upwardly from a connection end portion of the connecting member, and a connection end portion of the thread hanging hook is provided with a connecting hole that is insertable into the pin from above the pin, and is drawable in an upward direction.
 12. The multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to claim 1, wherein the left needle plate base or the sewing machine bed comprise protruding knock pins for positioning the left needle plate base to the sewing machine bed at a plurality of positions away from a plurality of fixedly connecting portions and connection release portions by the screw members, and wherein the sewing machine bed or the left needle plate base is provided with pin holes engageable with the knock pins.
 13. The multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to claim 1, wherein a target sewing machine is a horizontal tube type single needle multi-thread chain stitch sewing machine.
 14. The multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to claim 1, wherein a target sewing machine is a horizontal tube type multi-needle multi-thread chain stitch sewing machine. 